Light emitting device, light emitting device package and lighting system

ABSTRACT

Disclosed are a light emitting device, a light emitting device package, and a lighting system. The light emitting device includes an oxide including gallium aluminum over a gallium oxide substrate, a nitride including gallium aluminum over the oxide including gallium aluminum, and a light emitting structure over the nitride including gallium aluminum.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119 to Korean PatentApplication No. 10-2009-0127189 filed Nov. 2, 2009, which is herebyincorporated by reference.

BACKGROUND

The embodiment relates to a light emitting device, a light emittingdevice package, and a lighting system.

A light emitting device (LED) includes a p-n junction diode having acharacteristic of converting electric energy into light energy. The p-njunction diode can be formed by combining group III and V elements ofthe periodic table. The LED can represent various colors by adjustingthe compositional ratio of compound semiconductors.

When forward voltage is applied to the LED, electrons of an n layer arebonded with holes of a p layer, so that energy corresponding to anenergy gap between a conduction band and a valance band may begenerated. This energy is mainly realized as heat or light, and the LEDemits the energy as the light.

A nitride semiconductor represents superior thermal stability and wideband gap energy, so the nitride semiconductor has been spotlighted inthe field of optical devices and high-power electronic devices. Inparticular, blue, green, and UV light emitting devices employing thenitride semiconductor have already been developed and extensively used.

Meanwhile, a light emitting device including the nitride semiconductorcan be classified into a lateral type light emitting device and avertical type light emitting device according to positions of electrodelayers.

However, the vertical type light emitting device has a difficulty in themanufacturing process because a non-conductive substrate has to beseparated after the nitride semiconductor has been formed over thenon-conductive substrate such as a sapphire substrate. Accordingly,researches and studies have been actively carried out toward a nitridesemiconductor light emitting device that does not require the separationof a substrate by using a conductive substrate when the vertical typelight emitting device is manufactured.

For example, according to the related art, a nitride semiconductor layermay be formed over a gallium oxide substrate.

However, according to the related art, the nitride semiconductor layermay be delaminated from the gallium oxide substrate.

For example, the gallium oxide is easily etched at a high temperaturehydrogen gas atmosphere, but the nitride semiconductor layer is grown ata high-temperature atmosphere of the mixture of ammonia gas and hydrogengas. Therefore, when the nitride semiconductor layer is grown, a portionof the interface between the gallium oxide substrate and the nitridesemiconductor layer is irregularly etched by hydrogen gas at a hightemperature. The irregular etching of the interface degrades theadhesive strength of the interface, thereby causing the delaminationbetween the nitride semiconductor layer and the gallium oxide substrate.

In addition, the gallium oxide substrate has a thermal expansioncoefficient different from that of the nitride semiconductor layer.Accordingly, when the nitride semiconductor layer is cooled after thenitride semiconductor layer has been grown, or when a heat treatmentprocess is performed in order to manufacture the light emitting device,the delamination may be caused at the interface between the galliumoxide substrate and the nitride semiconductor layer due to the stresscaused by the difference in the thermal expansion coefficient betweenthe gallium oxide substrate and the nitride semiconductor layer.

BRIEF SUMMARY

The embodiment provides a nitride semiconductor light emitting devicecapable of representing high performance by realizing a high-qualitynitride semiconductor layer over a gallium oxide substrate, a lightemitting device package, and a lighting system.

According to the embodiment, a light emitting device includes an oxideincluding gallium aluminum over a gallium oxide substrate, a nitrideincluding gallium aluminum over the oxide including gallium aluminum,and a light emitting structure over the nitride including galliumaluminum.

According to the embodiment, the light emitting device package includesa package body, third and fourth electrode layers installed over thepackage body, and a light emitting device electrically connected to thethird and fourth electrode layers.

According to the embodiment, the lighting system includes a substrate,and a light emitting module including a light emitting device packageinstalled over the substrate. The light emitting device package includesa package body, third and fourth electrode layers installed over thepackage body, and a lighting emitting device according to claim 1 andelectrically connected to the third and fourth electrode layers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a light emitting device according tothe embodiment;

FIGS. 2 to 6 are sectional views showing a method of manufacturing thelight emitting device according to the embodiment;

FIG. 7 is a sectional view showing a light emitting device packageaccording to the embodiment;

FIG. 8 is a perspective view showing a lighting unit according to theembodiment; and

FIG. 9 is an exploded perspective view showing a backlight unitaccording to the embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a light emitting device, a light emitting device package,and a lighting system according to the embodiment will be described withreference to accompanying drawings.

In the description of embodiments, it will be understood that when alayer (or film) is referred to as being ‘on’ another layer or substrate,it can be directly over another layer or substrate, or interveninglayers may also be present. Further, it will be understood that when alayer is referred to as being ‘under’ another layer, it can be directlyunder another layer, and one or more intervening layers may also bepresent. In addition, it will also be understood that when a layer isreferred to as being ‘between’ two layers, it can be the only layerbetween the two layers, or one or more intervening layers may also bepresent.

Embodiment

FIG. 1 is a sectional view showing a light emitting device 100 accordingto the embodiment.

The light emitting device 100 may include a gallium aluminum oxide 110over a gallium oxide substrate 105, a gallium aluminum nitride 120 overthe gallium aluminum oxide 110, and a light emitting structure 130 overthe gallium aluminum nitride 120.

The gallium aluminum oxide 110 may include Ga_(x)Al_(y)O_(z) (0<x≦1,0<y≦1, 0<z≦1), but the embodiment is not limited thereto.

The gallium aluminum nitride 120 may include Ga_(x)Al_(y)N_(z) (0<x≦1,0<y≦1, 0<z≦1), but the embodiment is not limited thereto.

The light emitting structure 130 may include a second conductivesemiconductor layer 132 over the gallium aluminum nitride 120, an activelayer 134 over the second conductive semiconductor layer 132, and afirst conductive semiconductor layer 136 over the active layer 134, butthe embodiment is not limited thereto.

According to the embodiment, the bond strength between gallium (Ga) andoxygen (O) is stronger than the bond strength between aluminum (Al) andoxygen (O), and the bond strength between gallium (Ga) and nitrogen (N)is stronger than the bond strength between aluminum (Al) and nitrogen(N).

Accordingly, the interfacial adhesion between the gallium aluminum oxide110 and the gallium aluminum nitride 120 is stronger than that betweenthe gallium oxide substrate and the light emitting structure 130including a nitride semiconductor layer. Accordingly, the light emittingstructure 130 can be prevented from being delaminated from the galliumoxide substrate 105. The interfacial adhesion between the galliumaluminum oxide 110 and the gallium aluminum nitride 120 is stronger thanthat between gallium oxide/gallium nitride and the nitride semiconductorlayer, so that delamination can be prevented.

According to the light emitting device and a method of manufacturing thesame according to the embodiment, as the interfacial adhesion betweenthe gallium oxide substrate and the nitride semiconductor layer isenhanced, the nitride semiconductor layer having high quality can berealized, so that a light emitting device having superior reliabilityand performance can be realized.

Hereinafter, the method of manufacturing the light emitting device 100according to the embodiment will be described with reference to FIGS. 2to 6.

As shown in FIG. 2, the gallium oxide substrate 105 is prepared. Thegallium oxide substrate 105 may include a conductive substrate. Thegallium oxide substrate 105 may include a Ga₂O₃ substrate, but theembodiment is not limited thereto.

The gallium oxide substrate 105 may have superior electricalconductivity through the doping of impurities.

A wet cleaning process is performed with respect to the gallium oxidesubstrate 105 to remove organic and inorganic materials from the galliumoxide substrate 105.

As shown in FIG. 3, the gallium aluminum oxide 110 is formed over thegallium oxide substrate 105. The gallium aluminum oxide 110 may includeGa_(x)Al_(y)O_(z)(0<x≦1, 0<y≦1, 0<z≦1), but the embodiment is notlimited thereto.

Since the bond strength between atoms is strongly represented in thegallium aluminum oxide 110, great energy gap is represented.Accordingly, since the gallium aluminum oxide 110 may have electricalconductivity less than that of the gallium oxide substrate 105, thegallium aluminum oxide 110 may be formed at a thickness of 1 or less,but the embodiment is not limited thereto.

In order to form the gallium aluminum oxide 110, a deposition processmay be performed with respect to the top surface of the gallium oxidesubstrate 105 by using a thin film deposition device. For example, thegallium aluminum oxide 110 may be formed through liquid-phase epitaxy,vapor phase epitaxy, molecular beam epitaxy, or sputtering.

In order to form the gallium aluminum oxide 110, an aluminum layer (notshown) is formed over the gallium oxide substrate 105. Thereafter, heattreatment is performed with respect to the resultant structure at anoxygen atmosphere, so that Al atoms of the aluminum layer are diffusedinto the gallium oxide substrate 105, thereby forming the galliumaluminum oxide 110.

For example, after an Al thin film layer has been formed over thegallium oxide substrate 105, oxygen gas or mixture gas mainly containingoxygen gas is injected into a chamber and heat treatment is performedwith respect to the gallium oxide substrate 105 at a temperature ofabout 500° C. to 1200° C., thereby forming the gallium aluminum oxide110. However, the embodiment is not limited thereto.

Thereafter, as shown in FIG. 4, the gallium aluminum nitride 120 isformed over the gallium aluminum oxide 110.

The gallium aluminum nitride 120 may include Ga_(x)Al_(y)N_(z) (0<x≦1,0<y≦1, 0<z≦1), but the embodiment is not limited thereto.

The gallium aluminum nitride 120 may be formed over the gallium aluminumoxide 110 by using a thin film deposition device. For example, thegallium aluminum nitride 120 may be formed through liquid-phase epitaxy,vapor phase epitaxy, molecular beam epitaxy, or sputtering, but theembodiment is not limited thereto.

The gallium aluminum nitride 120 may be formed by nitrifying a portionof the gallium aluminum oxide 110.

For example, an aluminum layer (not shown) is formed over the galliumoxide substrate 105. Thereafter, heat treatment is performed withrespect to the resultant structure at an oxygen atmosphere, so that Alatoms of the aluminum layer are diffused into the gallium oxidesubstrate 105, thereby forming the gallium aluminum oxide 110. Next, thegallium aluminum oxide 110 is nitrified at a high temperature and at anammonia atmosphere, so that the gallium aluminum nitride 120 can beformed.

The high-temperature nitrification can be performed by injecting ammoniagas, the mixture of ammonia gas and oxygen gas, or the mixture ofammonia gas and nitrogen gas into a chamber.

In this case, impurity gas is injected into the chamber, so that theelectrical conductivity of the gallium aluminum nitride 120 can beimproved.

According to the embodiment, the bond strength between gallium (Ga) andoxygen (O) is stronger than that between aluminum (Al) and oxygen (O),and the bond strength between gallium (Ga) and nitrogen (N) is strongerthan that between aluminum (Al) and nitrogen (N).

Accordingly, the interfacial adhesion between the gallium aluminum oxide110 and the gallium aluminum nitride 120 is stronger than that betweenthe gallium oxide substrate 105 and the light emitting structure 130including a nitride semiconductor layer. Therefore, the delaminationbetween the gallium oxide substrate 105 and the light emitting structure130 can be prevented.

According to the light emitting device and the method of manufacturingthe same according to the embodiment, as the interfacial adhesionbetween the gallium oxide substrate and the nitride semiconductor layeris enhanced, the nitride semiconductor layer having high quality can berealized, so that a light emitting device having superior reliabilityand performance can be realized.

Then, the light emitting structure 130 may be formed over the galliumaluminum nitride 120 as shown in FIG. 5. FIG. 6 is an enlarged viewshowing a portion of the light emitting structure 130.

The light emitting structure 130 may include the second conductivesemiconductor layer 132 formed over the gallium aluminum nitride 120,the active layer 134 formed over the second conductive semiconductorlayer 132, and the first conductive semiconductor layer 136 formed overthe active layer 134, but the embodiment is not limited thereto.

The first conductive semiconductor layer 136 may include group III-Vcompound semiconductors doped with first conductive dopants. When thefirst conductive semiconductor layer 136 is an N type semiconductorlayer, the first conductive dopants may include Si, Ge, Sn, Se, or Te asN type dopants, but the embodiment is not limited thereto.

The first conductive semiconductor layer 136 may include a semiconductormaterial having a composition formula of In_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1,0≦y≦1, 0≦x≦1).

The first conductive semiconductor layer 136 may include at least oneselected from the group consisting of InN, AlN, InGaN, AlGaN, InAlGaN,AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, and InP.

The first conductive semiconductor layer 136 may include an N type GaNlayer through CVD (chemical vapor deposition), MBE (molecular beamepitaxy), sputtering, or HVPE (hydride vapor phase epitaxy). Inaddition, the first conductive semiconductor layer 136 may be formed byinjecting trimethyl gallium (TMGa) gas, ammonia (NH₃) gas, nitrogen (N₂)gas, or silane (SiH₄) gas including N type impurities such as Si into achamber.

The active layer 134 emits a light having energy determined by anintrinsic energy band of materials constituting the active layer (lightemitting layer) through the combination of electrons injected throughthe first conductive semiconductor layer 136 and holes injected throughthe second conductive semiconductor layer 132.

The active layer 134 may have one of a SQW (single quantum well)structure, an MQW (multi-quantum well) structure, a quantum-wirestructure, or a quantum dot structure. For example, the active layer 134may have the MQW structure by injecting TMGa gas, NH₃ gas, N₂ gas orTMIn gas, but the embodiment is not limited thereto.

The active layer 134 may have a well/barrier layer including at leastone of InGaN/GaN, InGaN/InGaN, GaN/AlGaN, InAlGaN/GaN, GaAs(InGaAs)/AlGaAs and GaP (InGaP)/AlGaP, but the embodiment is not limitedthereto. The well layer may include a material having the band gapenergy lower than that of the barrier layer.

A conductive clad layer (not shown) can be formed over and/or under theactive layer 134. The conductive clad layer may include an AlGaN-basedsemiconductor having the band gap energy higher than that of the activelayer 134.

The second conductive semiconductor layer 132 may include the groupIII-V compound semiconductor doped with the second conductive dopant.For instance, the second conductive semiconductor layer 132 may includethe semiconductor material having the composition formula ofIn_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1). In detail, the secondconductive semiconductor layer 132 may include one selected from thegroup consisting of GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, AlGaAs,GaP, GaAs, GaAsP, and AlGaInP. If the second conductive semiconductorlayer 132 is a P type semiconductor layer, the second conductive dopantincludes the P type dopant such as Mg, Zn, Ca, Sr, or Ba. The secondconductive semiconductor layer 132 can be prepared as a single layer ora multiple layer, but the embodiment is not limited thereto.

The second conductive semiconductor layer 132 may include a P type GaNlayer, which can be formed by injecting TMGa gas, NH₃ gas, N₂ gas and(EtCp₂Mg) {Mg(C₂H₅C₅H₄)₂} gas including p type impurities (for example,Mg) into the chamber, but the embodiment is not limited thereto.

According to the embodiment, the first conductive semiconductor layer136 may include an N type semiconductor layer and the second conductivesemiconductor layer 136 may include a P type semiconductor layer. Thefirst conductive semiconductor layer 136 may include a P typesemiconductor layer and the second conductive semiconductor layer 136may include an N type semiconductor layer.

In addition, a semiconductor layer, such as an N type semiconductorlayer (not shown) having polarity opposite to that of the secondconductive semiconductor layer 132, can be formed over the secondconductive semiconductor layer 132. Thus, the light emitting structure130 may include one of an N—P junction structure, a P—N junctionstructure, an N—P—N junction structure, and a P—N—P junction structure.

Thereafter, a second electrode (not shown) may be formed under thegallium oxide substrate 105, and a first electrode (not shown) may beformed over the first conductive semiconductor layer 136.

The second electrode may include an ohmic layer (not shown), areflective layer (not shown), or a conductive support substrate (notshown).

For example, the second electrode may include an ohmic layer, and mayhave a multi-stack structure of single metal, metallic alloy, ormetallic oxide such that hole injection can be efficiently performed.

For example, the ohmic layer may include at least one selected from thegroup consisting of ITO (indium tin oxide), IZO (indium zinc oxide),IZTO (indium zinc tin oxide), IAZO (indium aluminum zinc oxide), IGZO(indium gallium zinc oxide), IGTO (indium gallium tin oxide), AZO(aluminum zinc oxide), ATO (antimony tin oxide), GZO (gallium zincoxide), IZON (IZO Nitride), AGZO (Al—Ga ZnO), IGZO (In—Ga ZnO), ZnO,IrOx, RuOx, NiO, RuOx/ITO, Ni/IrOx/Au, Ni/IrOx/Au/ITO, Ag, Ni, Cr, Ti,Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and Hf, but the embodiment is notlimited thereto.

For example, the reflective layer may include a metal or a metal alloyincluding at least one selected from the group consisting of Ag, Ni, Al,Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and Hf. In addition, the reflectivelayer can be prepared as a multiple layer by using the above metal ormetal alloy and transmissive conductive material, such as IZO, IZTO,IAZO, IGZO, IGTO, AZO, or ATO. For instance, the reflective layer mayhave the stack structure including IZO/Ni, AZO/Ag, IZO/Ag/Ni, AZO/Ag/Ni.

In addition, a conductive support substrate may include at least oneselected from the group consisting of copper (Cu), a Cu alloy, gold(Au), nickel (Ni), molybdenum (Mo), copper-tungsten (Cu—W), and acarrier wafer (for example, Si, Ge, GaAs, GaN, ZnO, SiGe, or SiC wafer).

According to the light emitting device of the embodiment, as theinterfacial adhesion between the gallium oxide substrate and the nitridesemiconductor layer is enhanced, the nitride semiconductor layer havinghigh quality can be realized, so that a light emitting device havingsuperior reliability and performance can be realized.

FIG. 7 is a view showing a light emitting device package 200 includingthe light emitting device 100 according to the embodiment.

Referring to FIG. 7, the light emitting device package 200 according tothe embodiment includes a package body 205, third and fourth electrodelayers 213 and 214 formed over the package body 205, the light emittingdevice 100 provided over the package body 205 and electrically connectedto the third and fourth 213 and 214 and a molding member 240 thatsurrounds the light emitting device 100.

The package body 205 may include silicon, synthetic resin or metallicmaterial. An inclined surface may be formed around the light emittingdevice 100.

The third and fourth electrode layers 213 and 214 are electricallyisolated from each other to supply power to the light emitting device100. In addition, the third and fourth electrode layers 213 and 214reflect the light emitted from the light emitting device 100 to improvethe light efficiency and dissipate heat generated from the lightemitting device 100 to the outside.

The vertical type light emitting device shown in FIG. 1 can be employedas the light emitting device 100, but the embodiment is not limitedthereto.

The light emitting device 100 can be installed over the package body 205or the third and fourth electrode layers 213 and 214.

The light emitting device 100 is electrically connected to the thirdelectrode layer 213 and/or the fourth electrode layer 214 through atleast one of a wire bonding scheme, a flip chip bonding scheme and a diebonding scheme. According to the embodiment, the light emitting device100 is electrically connected to the third electrode layer 213 through awire 230 and electrically connected to the fourth electrode layer 214through the die bonding scheme.

The molding member 240 surrounds the light emitting device 100 toprotect the light emitting device 100. In addition, the molding member240 may include phosphors to change the wavelength of the light emittedfrom the light emitting device 100.

A plurality of light emitting device packages according to theembodiment may be arrayed over a substrate, and an optical memberincluding a light guide plate, a prism sheet, a diffusion sheet or afluorescent sheet may be provided over the optical path of the lightemitted from the light emitting device package. The light emittingdevice package, the substrate, and the optical member may serve as abacklight unit or a lighting unit. For example, the lighting system mayinclude a backlight unit, a lighting unit, an indicator, a lamp or astreetlamp.

FIG. 8 is a perspective view showing a lighting unit 1100 according tothe embodiment. The lighting unit 1100 shown in FIG. 9 is an example ofa lighting system, and the embodiment is not limited thereto.

Referring to FIG. 8, the lighting unit 1100 includes a case body 1110, alight emitting module 1130 installed in the case body 1110, and aconnection terminal 1120 installed in the case body 1110 to receivepower from an external power source.

Preferably, the case body 1110 includes material having superior heatdissipation property. For example, the case body 1110 includes metallicmaterial or resin material.

The light emitting module 1130 may include a substrate 1132 and at leastone light emitting device package 200 installed over the substrate 1132.

The substrate 1123 includes an insulating member printed with a circuitpattern. For instance, the substrate 1132 includes a PCB (printedcircuit board), an MC (metal core) PCB, an F (flexible) PCB, or aceramic PCB.

In addition, the substrate 1132 may include material that effectivelyreflects the light. The surface of the substrate 1132 can be coated witha color, such as a white color or a silver color, to effectively reflectthe light.

At least one light emitting device package 200 can be installed over thesubstrate 1132. Each light emitting device package 200 may include atleast one light emitting device 100. The light emitting device 100 mayinclude a colored LED that emits the light having the color of red,green, blue or white and a UV (ultraviolet) LED that emits UV light.

The light emitting device packages 200 of the light emitting module 1130can be variously arranged to provide various colors and brightness. Forexample, the white LED, the red LED and the green LED can be arranged toachieve the high color rendering index (CRI).

The connection terminal 1120 is electrically connected to the lightemitting module 1130 to supply power to the light emitting module 1130.The connection terminal 1120 has a shape of a socket screw-coupled withthe external power source, but the embodiment is not limited thereto.For example, the connection terminal 1120 can be prepared in the form ofa pin inserted into the external power source or connected to theexternal power source through a wire.

FIG. 9 is an exploded perspective view showing a backlight unit 1200according to the embodiment. The backlight unit 1200 shown in FIG. 9 isan example of a lighting system and the embodiment is not limitedthereto.

The backlight unit 1200 according to the embodiment includes a lightguide plate 1210, a light emitting module 1240 for providing the lightto the light guide plate 1210, a reflective member 1220 positioned underthe light guide plate, and a bottom cover 1230 for receiving the lightguide plate 1210, light emitting module 1240, and the reflective member1220 therein, but the embodiment is not limited thereto.

The light guide plate 1210 diffuses the light to provide surface light.The light guide 1210 includes transparent material. For example, thelight guide plate 1210 can be manufactured by using acryl-based resin,such as PMMA (polymethyl methacrylate), PET (polyethyleneterephthalate), PC (polycarbonate), COC (cycloolefin copolymer) or PEN(polyethylene naphthalate) resin.

The light emitting module 1240 supplies the light to the lateral side ofthe light guide plate 1210 and serves as the light source of the displaydevice including the backlight unit.

The light emitting module 1240 can be positioned adjacent to the lightguide plate 1210, but the embodiment is not limited thereto. In detail,the light emitting module 1240 includes a substrate 1242 and a pluralityof light emitting device packages 200 installed over the substrate 1242and the substrate 1242 can be adjacent to the light guide plate 1210,but the embodiment is not limited thereto.

The substrate 1242 may include a printed circuit board (PCB) having acircuit pattern (not shown). In addition, the substrate 1242 may alsoinclude a metal core PCB (MCPCB) or a flexible PCB (FPCB) in addition tothe PCB, but the embodiment is not limited thereto.

In addition, the light emitting device packages 200 are arranged suchthat light exit surfaces of the light emitting device packages 200 arespaced apart from the light guide plate 1210 at a predetermineddistance.

The reflective member 1220 is disposed under the light guide plate 1210.The reflective member 1220 reflects the light, which travels downwardthrough the bottom surface of the light guide plate 1210, toward thelight guide plate 1210, thereby improving the brightness of thebacklight unit. For example, the reflective member 1220 may include PET,PC or PVC resin, but the embodiment is not limited thereto.

The bottom cover 1230 may receive the light guide plate 1210, the lightemitting module 1240, and the reflective member 1220 therein. To thisend, the bottom cover 1230 has a box shape with an open top surface, butthe embodiment is not limited thereto.

The bottom cover 1230 can be manufactured through a press process or anextrusion process by using metallic material or resin material.

According to the light emitting device, the light emitting devicepackage, and the lighting system of the embodiment, as the interfacialadhesion between the gallium oxide substrate and the nitridesemiconductor layer is enhanced, the nitride semiconductor layer havinghigh quality can be realized, so that a light emitting device havingsuperior reliability and performance can be realized.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

1. A light emitting device comprising: an oxide including galliumaluminum over a gallium oxide substrate; a nitride including galliumaluminum over the oxide including gallium aluminum; and a light emittingstructure over the nitride including gallium aluminum.
 2. The lightemitting device of claim 1, wherein the oxide including gallium aluminumcomprises Ga_(x)Al_(y)O_(z) (0<x<1, 0<y<1, 0<z≦1).
 3. The light emittingdevice of claim 1, wherein the oxide including gallium aluminum has athickness of 1 or less.
 4. The light emitting device of claim 1, whereinthe nitride including gallium aluminum comprises Ga_(x)Al_(y)N_(z)(0<x<1, 0<y≦1, 0<z≦1)
 5. The light emitting device of claim 1, whereinthe light emitting structure comprises: a second conductivesemiconductor layer over the nitride including gallium aluminum; anactive layer over the second conductive semiconductor layer; and a firstconductive semiconductor layer over the active layer.
 6. A lightemitting device package comprising: a package body; third and fourthelectrode layers over the package body; and a light emitting deviceclaimed in claim 1 and electrically connected to the third and fourthelectrode layers.
 7. A lighting system comprising: a substrate; and alight emitting module including a light emitting device package over thesubstrate, wherein the light emitting device package comprises a packagebody, third and fourth electrode layers over the package body, and alighting emitting device claimed in claim 1 and electrically connectedto the third and fourth electrode layers.